1. Field of the Invention
The present invention relates generally to nesting structures for wild birds and more particularly to an externally wall-mounted, laterally disposed elongated nesting structure acceptable to, selective for and protective of northern rough-winged swallows, which formerly have been known to commonly nest only in cavities within earthen cliffs, banks, excavations and piles, or in cavities within retaining walls, bridge foundations and building walls.
2. Description of the Prior Art
Northern rough-winged swallows once nested only in natural settings, such as in the upright earthen banks of rivers, lakes, oceans, or eroded earthen cliffs. These upright banks or cliffs are inaccessible to some, but not all, predators. In such natural settings these swallows burrow directly into the broad, upright earthen face and deep into the earth behind the exposed face. Though such burrows may be irregular where stones and roots redirect the digging, they are generally substantially horizontal from front to back and generally perpendicular to any substantially planar surface around the burrow entrance.
In such natural settings rough-winged swallows build their grassy, leafy nests at the back ends of such long burrows, a safe distance away from whatever weather and predators might be at, or outside, the bank face.
In natural settings, rough-winged swallows will also nest in burrows previously dug by bank swallows and kingfishers, again placing their nests deep within the earth and away from the exposed upright bank face.
In semi-natural settings, rough-winged swallows nest in burrows dug into upright faces created by earth-moving equipment in road cuttings, excavations and earthen piles and even sawdust piles, here yet again placing their nests deep within the earth or deep within the mass of piled particulate material and well away from the exposed upright face.
Northern rough-winged swallows have commonly nested in artificial settings where exterior upright artificial surfaces such as vertical retaining walls, bridge foundations and building walls simulate the broad, upright natural bank or cliff faces described above, and cavities through and behind these exterior upright surfaces simulate their nesting burrows.
A common artificial nesting setting for northern rough-winged swallows is within small diameter drain pipes set low in concrete retaining walls or bridge foundations along rivers or other bodies of water. Such pipes are substantially perpendicular to the planar exterior surface of the retaining wall but are often inclined slightly to drain water from the earth behind the wall, through the length of pipe and out through the exterior face. Rough-winged swallows, entering through the hole in the retaining wall exterior face, travel through the length of the drain pipe and typically build their nest at the interior end of the pipe, well beyond the plane of the exterior upright wall face.
Nests in the earth or in pipe buried in the earth behind a concrete or other permanent retaining wall are practically inaccessible to humans interested in research or breeding management such as trapping alien birds which usurp nests or controlling parasites which infest such nests.
Nests in retaining wall or bridge foundation drainage pipes are often destroyed in the breeding season when heavy spring rains raise rivers and streams above the level of these low-lying drainage pipes. Even normal rainfall, after draining through the earth behind retaining walls, will dampen nests as water trickles out through such drainage pipes.
Other less common artificial nesting settings are within deep crevices in stone retaining walls and within cavities behind and enterable through small openings in exterior building walls. Nests in these settings, being situated behind the exterior surfaces of such walls, are also inaccessible to humans interested in research or breeding management.
Stone walls so loosely built or buildings so dilapidated as to offer deep cavities to swallows also enable predators, such as rats, to travel within the walls to access the nests.
It is impractical to create nesting sites for rough-winged swallows in existent masonry retaining walls as one would have to drill through such walls and the nests would still be inaccessible to those interested in research or breeding management.
Finally, rough-winged swallows are not known to accept conventional bird houses.
It is, in general, an object of the present invention to provide an artificial, man-made nesting structure which is mountable on the exterior exposed surface of an artificial wall, is configured to blend in with the surface of the wall to attract the attention of northern rough-winged swallows without attracting avian competitors or human vandals, is adjustably mountable to protect a nesting from flood waters or avian competitors, is passively protective of the nesting, permits convenient internal access for non-disruptive, protective, active human management and research of the occupied enclosed nest, and is economical to create and maintain for annual reuse, as specified in the further objects stated below.
It is a further object of the present invention to provide a nesting cavity highly acceptable to northern rough-winged swallows, a species not known to commonly accept bird houses.
It is a still further object of the present invention to provide a self-contained nesting structure which may be externally mounted on the exposed face of a retaining wall or bridge foundation.
It is a still further object of the present invention that this externally wall-mounted structure contain a nesting chamber for northern rough-winged swallows, a species previously known to commonly nest only behind the exposed planar face or exposed broad surface of formations such as retaining walls or upright earthen banks.
It is yet a further object of the present invention to provide an elongated and substantially horizontal nesting cavity parallel to, and outside of, the wall face rather than perpendicular to, and behind, the wall face, yet still satisfying the instinct of these swallows to build nests distant from the cavity entrance.
It is yet a further object of the present invention to provide a rough-winged swallow nesting structure accessibly locatable external to the face of a retaining wall or bridge foundation, and thus permitting convenient, non-disruptive access to the nesting cavity through an easily removable and replaceable nest access door, to allow research and active human management of the nesting cavity such as trapping of destructive competitors or removal of parasites and old nests.
It is a still further object of the present invention that this externally wall-mounted structure will appear to blend in with the wall on which it is mounted, so that it might be misperceived by rough-winged swallows to be part of that wall, and so that the nesting cavity formed within the present invention might be misperceived by such swallows to be formed within the wall on which the structure is mounted.
It is yet a further object of the present invention that the shape of the nesting structure also might cause vandals to ignore the nesting structure when misperceiving it as part of the wall on which it is mounted.
It is a further object of the present invention that the shape of the nesting structure will discourage predators from resting upon it or entering it.
It is a further object of the present invention that the entrance in relation to the shape of the nesting structure will be noticeable and accessible to low-flying swallows, and less noticeable and less accessible to high-flying birds of other competing species.
It is a still further object of the present invention to provide a wall-mounted rough-winged swallow nesting structure which, unlike fixed retaining wall drainage pipes, may be ideally mounted above river flood waters yet close to such waters to favor swallows over other species which fly higher when over water.
It is a yet further object of the present invention to provide a manually height adjustable mounting mechanism, permitting convenient raising or lowering of the nesting structure relative to rising or falling river water levels, or to facilitate human access.
It is also a further object of the present invention to provide an automatically adjustable height mounting mechanism by which raising or lowering the nesting structure is accomplished by a flotation device in the rising or falling water.
It is a further object of the present invention to provide ventilation within the nesting structure without admitting excess light, which might repel swallows used to nesting in dark, dead-end tunnels, and to provide a sun shield to shade the structure from the sun.
It is a still further object of the present invention to provide various embodiments to suit the inclined walls of bridge arches, etc.
Lastly, it is a still further object of the present invention to provide an artificial structure which is economical to fabricate from materials light in weight and easy to work with, such as wood, plastic or metal.
The present invention fulfills the foregoing objects in specific ways to be described further below of the general form and function of the preferred embodiment: a planar structural back board member, such as a board, which is longer than it is wide, and which is relatively thin, with parallel edges and ends, is oriented so that its length is substantially horizontal, its width is substantially vertical, and the plane of the back board member surface is substantially parallel to the plane or broad upright surface of the wall or bridge foundation on which it will be mounted.
Attached upon and parallel to the long upper edge of this back board member is the long back edge of a roof member. This planar roof member, such as a board, is approximately the same length as the back board member, is longer than it is wide, is relatively thin, with parallel edges and ends, is oriented so that its length is substantially horizontal, its width sloping downward and forward from its line of attachment to the back board, ideally at about a 45-degree angle to the back board member.
The long, lower front edge of this sloping roof member is attached upon, and parallel to, the long upper front edge of a front wall member. This planar front wall member, such as a board, is approximately the same length as the back board and roof members, is longer than it is wide, is relatively thin, with parallel edges and ends, is oriented so that its length is substantially horizontal, its width sloping downward and backward from its line of attachment to the roof member, ideally at about a 90-degree angle to the roof member.
The long lower back edge of this sloping front wall member is attached beneath, and parallel to, the long lower edge of the back board member, ideally at about a 45-degree angle to the back board member.
The back board, roof, and front wall together form a substantially horizontal, elongated hollow structure which is triangular in cross-section or end view.
The nesting cavity formed by the substantially horizontal, elongated structure is at least 1xc2xe as long as it is high or wide, and preferably 4 to 6 times as long as it is high and is so configured to meet a basic instinct of rough-winged swallows: to nest within substantially horizontal elongated cavities.
The triangular configuration, with the back board closely parallel to the retaining wall on which it is to be mounted, with the roof at an obtuse angle to the retaining wall above, and with the front wall at an obtuse angle to the retaining wall below, unobtrusively forms a three-dimensional volume on the two-dimensional surface of the retaining wall, thereby being likely to be seen as part of that retaining wall by rough-winged swallows which previously commonly nest only behind the face of such walls.
By providing a substantially horizontal elongated nesting cavity which runs along a retaining wall, external to the exterior surface of such a wall, which may be misperceived as part of such a wall by rough-winged swallows, an important overall object of the present invention is attained: to provide a nesting structure highly acceptable to rough-winged swallows which is not dependent on such a retaining wall to provide the nesting cavity, but is only dependent on the retaining wall to provide a broad, upright surface by which to initially attract rough-winged swallows, and on which to mount the present invention.
By attaining this important object of the present invention, many of the other objects listed below are made possible.
Continuing with an embodiment of the present invention, a floor member within the elongated hollow structure is attached between the lower inner surface of the back board and the inner surface of the front wall to create a substantially level floor above the acutely angled intersection of the upright back board and the sloping front wall.
A similar ceiling member within the elongated hollow structure is attached between the upper inner surface of the back board and the inner surface of the roof to create a substantially level ceiling below the acutely angled intersection of the upright back board and the sloping roof.
The narrow planar floor and ceiling members, which can be wood strips, are nearly the same length as the back board, roof, and front wall, are longer than they are wide, with parallel long edges and ends, these long edges angled to suit attachment to the upright back board and the sloping front wall or sloping roof as may apply.
The nesting cavity within the elongated, substantially horizontal nesting structure is below the ceiling and above the floor.
This nesting cavity is enclosed with a five-sided panel located at the opposite ends of the elongated structure, creating a dark interior enterable by rough-winged swallows only through an entrance to be described below. This dark interior is attractive to these birds which typically nest in long, dark, dead-end burrows or pipes set in earth or concrete.
The empty spaces below the floor and above the ceiling partially isolate the nesting cavity from the radiant heat of the sun reflected off of water below or radiated directly from the sun above, reducing heat buildup to accommodate these birds which typically nest in the cool earth or cool concrete.
The empty spaces below the floor and above the ceiling are left open at the opposite ends of the elongated structure, permitting ventilation of these spaces to the outside.
To provide more cooling of the nesting cavity, air passages are formed in the center portion of the elongated ceiling. Fresh cool air may enter through the swallow entrance near one end of the elongated nesting cavity to replace the internal air warmed by solar radiation on the front wall and roof, rising through passages in the center portion of the ceiling, passing through the empty space above the ceiling, and exiting through the upper end openings.
The air flow up through the center portion of the ceiling bypasses the nest built at the end opposite the entrance, thereby cooling the interior without creating a direct harmful draft on the nest itself.
Any light which enters the nesting cavity through the upper ventilating features of the present invention would be negligible, indirect, diffuse, and not emanating from the end opposite the bird entrance. This dead-end darkness achieves the object of simulating the protective, nearly complete enclosure which rough-winged swallows have around their nests at the inner end of natural burrows or drainage pipes.
An optional thin planar sheet, such as sheet metal or sheet of opaque plastic, corresponding to the shape of the roof, and removably positioned parallel to the plane of the roof, but with a space between it and the roof, maintains the overall configuration of the nesting structure, while shielding the roof from direct sunlight in very sunny locations. This optional sun shield helps to maintain a cooler nesting cavity for these birds which are accustomed to nesting in the cool earth.
The steeply sloped roof or parallel sun shield is difficult for predators such as sea gulls, ravens or rats to rest upon.
The undercut and steeply sloped front wall is resistant to such predators as well.
The overall configuration of the present invention, which is intended to unobtrusively blend with the retaining wall, is not likely to attract the attention of vandals when such nesting structures are mounted in public places along rivers, lakes, and harbors.
The location of the entrance to the nesting structure in relation to the exterior shape of the structure is an important factor in fulfilling an important object which is to provide a nesting structure which discriminates in favor of northern rough-winged swallows over alien nesting competitors such as English sparrows and European starlings. The bird entrance to the structure is an opening formed in the upper portion of the undercut sloping front wall, near one end of the nesting structure. This entrance, being on the underside of the nesting structure is more visible to low-flying rough-winged swallows, which are very comfortable skimming over the surface of water, but less visible to higher-flying sparrows and starlings which would otherwise usurp the nesting site. The entrance in the undercut, sloping front wall is also more easily approached in flight by agile swallows than by less agile sparrows and starlings. An adjustable angle tail brace can be included to ease entry for rough-winged swallows when alien competition is of less concern than ease of entry for swallows themselves. Also, the present invention is equipped to permit more convenient trapping of such aliens.
The present invention, unlike fixed preexistent drain pipes, etc., may be ideally mounted on a retaining wall, etc., close to the water level to favor rough-winged swallows over sparrows and starlings.
The present invention, again unlike fixed preexistent drain pipes, etc., may be ideally mounted on a retaining wall, etc., above the historical or usual high-water mark to protect rough-winged swallows from tides and flood waters.
An embodiment of the present invention further fulfills the objects by discriminating in favor of low-flying rough-winged swallows while protecting them from rising flood waters by including a sliding adjustable mounting device which conveniently permits the human manager to manually raise or lower the nesting structure to maintain a mounting height close to, but safely above, such rising or falling water levels.
In another embodiment, a flotation device can be provided in rising or falling water below the nesting structure to control the raising or lowering of the nesting structure thereabove.
Various embodiments of the present invention may include modifications to adapt the nesting structure to certain settings such as the inclined surfaces of bridge arches, or the partially enclosed walls within concrete culverts.
The present invention fulfills an object by being economically made of light, easy to work with materials, such as wood, metal, or plastic, rather than the bulky, heavy masonry or earth which rough-winged swallows typically make their nests in.
As a self-contained nesting unit, the present invention may be located in many places where existent retaining walls and bridge foundations offer no existent nesting cavities at all, and thus the present invention may create a presence of rough-winged swallows where they were previously absent.
A very important object of the present invention is fulfilled by providing a rough-winged swallow nesting structure which is accessibly mounted outside the exposed surface of a retaining wall or bridge foundation, etc. A nesting area access opening for access by researchers and wildlife managers is formed in the roof at the end of the nesting structure opposite the end at which the bird entrance is formed. A nesting area access door is removeably and replaceably fitted into this nest access opening, or over this opening, to enclose the nesting chamber. The nest access opening and door permit human access for research, photography, and active beneficial management such as removal of parasites or trapping of alien birds.